阻燃剂类型对聚碳酸酯阻燃性能的影响

Effect of Flame Retardant Type on Flame Retardancy of Polycarbonate

分别选用溴化齐聚物、磺酸盐、聚硅氧烷混合物和磷酸酯阻燃剂对聚碳酸酯(PC)进行阻燃改性,研究了阻燃剂类型对PC阻燃性能的影响,同时探讨了试样厚度对阻燃性能测试结果的影响。结果表明,溴化齐聚物提升了PC的灼热丝起燃温度(GWIT),磺酸盐、聚硅氧烷混合物和磷酸酯降低了PC的GWIT;成炭对起燃的影响远小于热分解,决定GWIT高低的因素是热分解温度,热分解温度越高,GWIT越高。磺酸盐分解的SO2促使PC交联形成的产物为层碳或石墨化结构,不仅隔热、隔氧、阻止气体流通,还具有导电性,是真炭层,磺酸盐阻燃改性PC的相比电痕化指数由纯PC的175 V降低至150 V;聚硅氧烷混合物、磷酸酯及其分解物形成的“炭层”仅具有类似炭层的作用,无导电性,对PC的电痕化性能无影响。添加四种阻燃剂后PC的灼热丝可燃性指数、垂直燃烧等级均有不同程度的提升,针焰试验结果变好。随着试样厚度增加,溴化齐聚物阻燃PC的GWIT升高,磺酸盐和磷酸酯阻燃PC的GWIT降低,聚硅氧烷混合物阻燃PC的GWIT无明显变化。随着试样厚度增加,四种阻燃剂阻燃PC的其它阻燃性能整体变好,但磷酸酯阻燃PC的垂直燃烧等级仍为V–1级。

The flame retardancy of polycarbonate(PC)was studied by adding various flame retardants,such as brominated oligomer,sulfonate,polysiloxane mixture and phosphate flame retardants.Besides,the influences of the thickness of the sample on flame retardancy were discussed.The results show that,the glow wire ignition temperature(GWIT)of PC is increased by brominated oligomer and decreased by sulfonate,polysiloxane mixture,phosphate.The main factor that determines the level of GWIT is thermal decomposition temperature,the impact of which on ignition largely outweighs that of char formation.The higher the thermal decomposition temperature is,the higher the GWIT is.The SO2 decomposed from sulfonate promotes the cross-linking of PC to form a layered carbon or graphitized structure,which not only insulates heat,oxygen,and prevents gas flow,but also has electrical conductivity.It should be noticed that the char layer is real,and the comparative tracking index(CTI)of PC is reduced from 175 V to 150 V by adding sulfonate flame retardant.The“char layer”,formed by the polysiloxane mixture or phosphate and its decomposition products,only has a part of function of char layer.There is no influence on conductivity and CTI in the“char layer”for flame retardant modified PC.All four kinds of flame retardants can improve the burning resistance of PC,in terms of the glow wire flammability index(GWFI),vertical burning level,and needle flame test result.As the thickness of the sample increases,the GWIT of the flame retardant modified PC is increased by adding brominated oligomer and reduced by sulfonate and phosphate,while the GWIT of PC flame retarded by polysiloxane mixture has no obvious change.With the increase of sample thickness,there is an overall rise in the GWFI,vertical burning rating,and needle test result of PC with adding brominated oligomer,sulfonate,polysiloxane mixture,and phosphate,but the vertical burning rating of the phosphate flame retarded PC is still V–1.